Question

explain the method required for separation of the mixture
a) common salt ,sand, Iodine

Answer 1

1. First heat the mixture in a closed flask, as iodine undergoes sublimation so it starts to form vapours on heating and changes from solid to gas and sticks to the cold surface of the flask.
2. Now you are left with the mixture of salt and sand. They can be separated on the basis of their solubility in water. Add water to the mixture and stir well. Salt dissolves in water whereas sand settles at the bottom. Now filter it, sand will be obtained as a residue and salt solution will be obtained as filtrate.
3. Now heat the salt solution on a water bath till all the water evaporates and salt is left behind. Thus we have separated all the components.
Hope it helps.. ask if you need diagram of the question, I will send it

Answer 2

both salt and iodine are soluble in water hence you can not use any of the technique that have been suggested to you so far.  

Unlike salt and sand, iodine upon heating sublimes. So you can heat the mixture and sublime iodine and condense iodine vapors using a sublimation apparatus. Now you can use water to separate salt and sand. Salt will dissolve in water and will leave sand behind. Then evaporate water from salt solution to get salt.